The working principle and key technologies for reliable design of EPS controller were analyzed. The signal processing circuit and the power drive circuit were hierarchically designed to improve the anti-jamming capability and reliability. The PWM frequency was selected considering the relationship between the PWM frequency and the natural frequency of the mechanical system, the influence on the armature current ripple and the noise impact on people. Meanwhile, the influence of switching current pulse on the safety of the transistors and the motor should be taken into account. Three MOS transistors were paralleled for the economy, the heat dissipation and the reliability. The heat dissipation flake and its relevant parameters were selected to improve the drive efficiency and the stable operation capability.